Aircraft such as the ones commonly utilized in military applications have demanding performance requirements. To meet these requirements, primary flight control surfaces such as the exhaust nozzle system which provides thrust vectoring of engine exhaust are being incorporated for increased maneuvering capability. To provide thrust vectoring, the primary flight control surface at the aft end of the engine generally consists of two nozzle flap panels each mounted to tube supports which in turn are mounted on bearings within the engine wall structure. With this arrangement, engine exhaust passes over the tube supports and is diverted by the nozzle flap panels.
On fighter aircraft that have two engines there is a desire to position the engines side-by-side. Moreover, it is highly desirable to position the engines as close together as possible to minimize aerodynamic drag and imposing asymmetric thrust upon the aircraft in the event of a single engine out condition, but one of the constraints of positioning the two engines side-by-side is at the end of the tube support for the nozzle flap panels. In this connection, envelope restrictions are imposed by the engine cowling.
Conventionally, a flight control surface such as a nozzle flap panel is operated by attaching a bell-crank to either end of the tube support. This bell-crank is then driven by linear hydraulic cylinders and, since the nozzle flap panels would be considered primary flight control surfaces, hydraulic redundancy is required. As a result, each nozzle flap panel is usually driven by tandem linear hydraulic cylinders.
Due to the envelope restriction on the inboard end of the tube support for the nozzle flap panels, the conventional solution requires the drive means to be located at one end only, e.g., the outboard end. However, driving from one end only, e.g., the outboard end, the tube support for the nozzle flap panels must be designed to be stiffer which adds weight that is undesirable due to its adverse effect on performance.
Accordingly, it has remained to provide a satisfactory actuation system that drives both ends of the tube support for the nozzle flap panels. This must be done, however, in a manner which reduces weight while also meeting the envelope restrictions and, preferably, by converting redundant aircraft hydraulic power into mechanical power utilized for driving the nozzle flap panels. Additionally, it would be highly desirable for the actuation system to be an integral part of the tube support buried within the engine exhaust area to facilitate maintainability considerations.
Among the prior attempts to provide actuation systems of various types is that disclosed in Boehringer et al U.S. Pat. No. 4,441,675 directed to a drive system for high-lift devices on aircraft having two power drive units arranged so as to force sum the outputs. However, the Boehringer et al '675 patent provides one of the power drive units at each end of a connecting torque tube system and entirely fails to even suggest an actuation system that is an integral part of the tube support for a nozzle flap panel.
Among various other actuation systems, planetary gearing, and power transmitting systems are those disclosed in Magnuson U.S. Pat. Nos. 4,430,909, Coutant 4,423,644, Winzeler 4,357,840, Michling 4,304,152, Nash 4,181,260, and Brand et al 4,136,580, although none of these patents is directed to an actuator system for a control surface such as a nozzle flap of an aircraft engine.
As a result, it has remained to overcome the above stated problems and accomplish the stated objects by providing an entirely new type actuator system.